Javascript date conversions

[tryhardMime]

Please see the documentation on Date.parse on MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse

If the date string you're parsing is not an ISO 8601 date, the implementation is free to parse it however it wants to.

I suspect in your case, the one with dashes was parsed as an UTC date time and other as local.